There is no law to prevent surrogacy in Britain but it is illegal for surrogates to advertise as they do in the US. The Human Fertilisation and Embryology Authority, which regulates infertility and IVF clinics in Britain, says that any offer of such treatment using a surrogate mother would be governed by strict guidelines. 

I ask Barrie what gave him and Tony the idea to have babies using surrogacy. "We just wanted a child back then and if we could have, we would have fostered or adopted," says Barrie. "Lesbians have proved for years that kids of same-sex couples can grow up fine, but we still get prejudice. Lots of people think we must be a couple of paedophiles."

To create Saffron and Aspen, both men's sperm was extracted and separated so that Tony would father the male children and Barrie the females. These samples were mixed with the egg donor's eggs to form embryos. Two embryos were implanted into the surrogate resulting in twins.

Four years later, the men decided to have another child and defrosted the last surviving original embryo. This was implanted in a different surrogate resulting in Orlando. But this embryo had originally split from Aspen's, which means that Aspen and Orlando are biological twins despite the age gap and share exactly the same DNA.

With no embryos left, and the original egg donor being considered too old to donate, the couple chose a 25-year-old model as a replacement from the catalogue supplied by the surrogacy service. They decided that this time they did not mind who was the biological father and both gave sperm samples. Two embryos were implanted in the same surrogate they had used to carry Orlando.

After their first set of twins was born, the Drewitt-Barlows successfully challenged the American authorities to become the first gay couple to have both their names on their children's birth certificates.

 "People said to us we should just accept the fact that it is unnatural for two men to have kids, but neither is growing a new liver, so we refused to give up. And why shouldn't we have our own children?" Barrie is clear, however, that having the children and challenging the law was not something they did for gay emancipation, but was a "completely selfish desire to be parents".

To find the egg donors, the couple spent hours looking through catalogues, commenting on their appearances in a way not dissimilar to choosing a new set of curtains.

Did they consider adopting children once the law changed to allow gay men to do so? "It's a bit like giving blood. I won't do it now because it used to be rejected [as a result of the assumption that gay men were more likely to be infected with HIV than heterosexuals]," says Barrie. "I would cut my nose off to spite my face and now that we can adopt I won't do it."